Some individuals meet gold-standard clinical criteria for ASD prior to age 5 but end up later in development with no symptoms of ASD, and IQ and adaptive skills in the average range. This study evaluates this ?optimal outcome? (OO) in two groups: (1) those who participated in our OO research study as teens, now young adults, allowing us to evaluate how they navigate the difficult transition into independence and young adulthood; and (2) those who were diagnosed by us with ASD at age two and re-evaluated at age four, now in their teens, allowing us to identify which of this cohort has achieved optimal outcome, and thus to identify early predictors of OO. Both cohorts are compared to age-, gender-, and NVIQ-matched individuals with current ASD and with typical development (TD). We hypothesize that the young adults with OO will experience mild delays in adult milestones such as finishing higher education and obtaining competitive employment, along with greater anxiety, especially simple phobias, and ADHD symptoms. We also hypothesize that early childhood predictors of OO will be milder social impairment, higher adaptive skills in social, communication, and motor domains, and fewer repetitive behaviors. We employ fMRI in the second cohort (n=50 per study group, total n=150) to measure the functional connectivity networks that are involved in social and language tasks, and that are observed during resting state, to investigate how neural mechanisms relate to the dramatic symptom change observed in OO. Drawing on prior imaging research, we hypothesize that, compared to both ASD and TD, the OO group will show compensatory (atypical) connectivity of extra-modular prefrontal cognitive control networks and right hemisphere homologues of left-hemisphere language regions during language and social processing and during resting state.